code: def add_metric(self, metric: Metric):
      self._metrics.append(metric)
      return self
  
imports: from typing import Dict
  from transformers import EvalPrediction
  from transformers.trainer_utils import PredictionOutput
  import pandas
  import torch
  import numpy
  from typing import Union
  import json
  import logging
label_desc: Use image node_id 2 for calling the MetricEnsemble obj's underlying member method code with example usage: obj.add_metric(metric) and returns: self